DiGeorge syndrome 2 is associated with a range of developmental and medical problems. Reported features can include congenital heart abnormalities, hypoparathyroidism, T-cell immunodeficiency and characteristic facial features.

Other possible features include microcephaly, abnormalities of the hands and feet, genitourinary abnormalities, developmental delay and hearing loss.

The clinical features can overlap with those seen in 22q11.2 deletion syndrome, although the underlying chromosomal abnormality and clinical presentation may differ.

1p36 deletion syndrome is a chromosomal condition that can be associated with characteristic facial features, developmental and intellectual disability, seizures, skeletal abnormalities and abnormalities affecting the brain and heart.

Some structural abnormalities may be visible during prenatal ultrasound, including certain heart defects or abnormalities affecting brain development. However, a normal ultrasound cannot exclude the condition.

The severity and long-term outlook can vary considerably between individuals.

Prader-Willi syndrome and Angelman syndrome involve abnormalities affecting the 15q11-q13 region of chromosome 15. The condition that develops depends partly on whether the affected genetic material was inherited from the mother or father.

Prader-Willi syndrome

Prader-Willi syndrome can cause severe low muscle tone and feeding difficulties during early infancy. Later features can include excessive appetite, obesity, developmental delay, learning difficulties, short stature and behavioural problems.

Prenatal ultrasound findings are often normal, although reduced fetal movement or breech presentation may sometimes be observed.

NIPT microdeletion screening can identify cases caused by a detectable deletion. However, not all cases of Prader-Willi syndrome are caused by a deletion, so screening for a deletion cannot identify every affected pregnancy.

Angelman syndrome

Angelman syndrome is associated with significant developmental delay, intellectual disability, severe speech impairment, movement and balance difficulties and seizures.

Prenatal ultrasound is usually normal.

As with Prader-Willi syndrome, only a proportion of Angelman syndrome cases are caused by a chromosomal deletion. Therefore, a negative microdeletion screening result cannot exclude all causes of Angelman syndrome.

Prader-Willi-like syndrome associated with the SIM1 region can have features resembling Prader-Willi syndrome.

Reported features can include reduced fetal activity, low muscle tone, obesity, developmental or intellectual disability, short stature, hormonal abnormalities affecting sexual development, and small hands and feet.

Cri-du-chat syndrome is caused by a deletion involving the short arm of chromosome 5.

Features can include developmental and intellectual disability, delayed speech and language development, microcephaly, characteristic facial features and congenital heart abnormalities.

Affected babies may also have a distinctive high-pitched cry during infancy, from which the condition gets its name.

The severity of the condition varies according to the size and location of the chromosomal deletion.

Wolf-Hirschhorn syndrome is associated with a deletion involving the short arm of chromosome 4.

Possible features include growth restriction beginning before birth, low muscle tone, characteristic facial features, microcephaly, developmental and intellectual disability, seizures and skeletal abnormalities.

Some individuals may also have congenital heart defects, hearing problems, urinary tract abnormalities or structural abnormalities affecting the brain.